On 2020/05/16 9:19, Bart Van Assche wrote:
> This patch suppresses an uninteresting KMSAN complaint without affecting
> performance of the null_blk driver if CONFIG_KMSAN is disabled.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
> Cc: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
> Cc: Alexander Potapenko <glider@xxxxxxxxxx>
> Reported-by: Alexander Potapenko <glider@xxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
> drivers/block/null_blk_main.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
> index 06f5761fccb6..df1e144eeaa4 100644
> --- a/drivers/block/null_blk_main.c
> +++ b/drivers/block/null_blk_main.c
> @@ -1250,8 +1250,38 @@ static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd,
> return errno_to_blk_status(err);
> }
>
> +static void nullb_zero_rq_data_buffer(const struct request *rq)
> +{
> + struct req_iterator iter;
> + struct bio_vec bvec;
> +
> + rq_for_each_bvec(bvec, rq, iter)
> + zero_fill_bvec(&bvec);
> +}
> +
> +static void nullb_zero_read_cmd_buffer(struct nullb_cmd *cmd)
> +{
> + struct nullb_device *dev = cmd->nq->dev;
> +
> + if (dev->queue_mode == NULL_Q_BIO && bio_op(cmd->bio) == REQ_OP_READ)
> + zero_fill_bio(cmd->bio);
> + else if (req_op(cmd->rq) == REQ_OP_READ)
> + nullb_zero_rq_data_buffer(cmd->rq);
> +}
Shouldn't the definition of these two functions be under a "#ifdef CONFIG_KMSAN" ?
> +
> +/* Complete a request. Only called if dev->memory_backed == 0. */
> static inline void nullb_complete_cmd(struct nullb_cmd *cmd)
> {
> + /*
> + * Since root privileges are required to configure the null_blk
> + * driver, it is fine that this driver does not initialize the
> + * data buffers of read commands. Zero-initialize these buffers
> + * anyway if KMSAN is enabled to prevent that KMSAN complains
> + * about null_blk not initializing read data buffers.
> + */
> + if (IS_ENABLED(CONFIG_KMSAN))
> + nullb_zero_read_cmd_buffer(cmd);
> +
> /* Complete IO by inline, softirq or timer */
> switch (cmd->nq->dev->irqmode) {
> case NULL_IRQ_SOFTIRQ:
>
--
Damien Le Moal
Western Digital Research
